1. Field of the Invention
The present invention relates to an anti-galling alloy with finely dispersed precipitates, more particularly to an anti-galling alloy comprising Ni, Cr, Sn, Bi, Mo, Fe, Si and Te, wherein the matrix has a fine dendritic structure and the Bi precipitates are finely dispersed on the dendritic structure, so that the anti-galling properties and physicochemical properties such as corrosion resistance and hardness can be significantly improved. The anti-galling alloy of the present invention will greatly contribute to the improvement in life cycle and mechanical precision of various wet machinery parts such as rotor, shaft, valve and mechanical sealing.
An anti-galling alloy refers to a metal that enables to maintain smooth surface when in contact with other metals, because it has a very low friction coefficient and prevents cracking due to contact stress. Therefore, anti-galling alloy has been widely used in industrial machineries having wet machinery parts which require frequent metal-metal contacts.
2. Description of the Related Art
Traditionally, lead-containing alloys have been used as anti-galling alloy. However, due to the harmfulness of lead to health, alloys containing no lead have been developed and used. Typical examples are Bi-containing Ni-matrix and Cu-matrix alloys [U.S. Pat. Nos. 3,145,099, 4,702,887, 5,242,657, 6,059,901 and 5,846,483].
Especially, the Ni—Cr—Sn—Bi based alloy has been known as suitable for use as rotor, shaft, valve and other mechanical sealing parts of driving machines, since it contains no lead and offers relatively good anti-galling properties. However, the Ni—Cr—Sn—Bi based alloy has insufficient abrasion resistance. Particularly, when it is in contact with stainless steel, its surface becomes scraped off roughly. The fast abrasion process results in reducing life cycle of a given material as well as impairing mechanical precision, so that it is not desirable to be used for wet parts or valves of various industrial machineries.
The key factors that determine the anti-galling properties are alloy composition and microstructure. Conventionally, researches have been focused on improvement of alloy compositions.